Tessa, 42, from London, was sitting on the sofa next to her son Tyler as he played popular game Fortnite when she heard the sound of a man's "giggles" coming from the TV speakers. After figuring out where the noise was coming from, she noticed the voice refer to her son as 'Danny' - the name the account is set up under.
According to Tessa, the unidentified man went from playful and encouraging - 'Put your headset on, Danny' - to creepy and sick - 'Do you know what sex is?' - in a matter of seconds. Horrified, she quickly stopped the game and muted the console. She's now issued a warning to parents to turn audio off completely if they want to protect their children from online paedophiles.
Children often wear headsets while playing the latest craze - a survival game featuring monsters and heroes - which is hugely popular with young people.
Tessa said: "Tyler doesn't have a headset so we were sure he wouldn't be hearing anything. There was no speaking for a couple of days. It was only when I was sitting with him as he played around 9:15pm when I heard these giggles. It was disgusting. He asked if 'Danny' had a fanny and knew what sex was. He was coaxing him to put his headset on. The tone of this person's voice was horrible. I immediately stopped it but it could have been much worse. What if Tyler had been playing in his bedroom or with a headset on? Thankfully it was installed downstairs but I would encourage everyone to turn the audio off completely."
Tessa said Tyler has recently been diagnosed with autism and has taken the incident badly. He wanted to sleep in her bed after the shock and asked: "Does he [the sick gamer] know where we live?"
On Tuesday, the National Crime Agency warned Fortnite is putting children at risk from online paedophiles.
Last month, a second furious mum unleashed her anger after hearing a man apparently trying to groom her son through the same game. The mother, from Liverpool, said she "felt sick to her stomach" when she heard the comments while her 12-year-old son played on the computer. The boy was playing on Fortnite when the man started asking him to send naked pictures and to perform sex acts on him, the Liverpool Echo reports.
He also said he would pay £50 and disturbingly told the youngster to "die slowly". The mum, who recorded the interaction, said she was watching soaps in her bedroom when she heard the "disgusting" questions and ran in to her son’s room.